A healthcare data acquisition device belonging of the prior art is shown in FIG. 16. On either side of device 200 are grips 205 and 206. In the two grips 205 and 206 are cylindrical current electrodes 201 and 202, respectively, which apply a current to a patient using the device. The two grips 205 and 206 further include measurement electrodes 203 and 204, respectively, which measure voltage across the body of the patient.
Prior to measurement, the patient uses input unit 210 to enter physical characteristics, for example, data such as height, weight, age and sex. To measure the impedance of the body, the patient holds grips 205 and 206 with both hands so that current electrodes 201 and 202 are in contact with the parts of the hands between the thumbs and the index fingers, and measurement electrodes 203 and 204 are in contact with the palms of the hands below the fourth and fifth fingers. By measuring the potential developed across the body due to its resistance with respect to the current which is applied, the impedance of the body can be obtained. The general relationship between the impedance of the body and data relating to healthcare such as percentage of body fat is stored in a data base obtained by statistical methods. Using this data base and the measured impedance of the body, data are obtained which can be useful in managing the healthcare of the patient.
With the electrode configuration of device 200, it was possible in the prior art to produce a small, light and inexpensive healthcare data acquisition device which could measure impedance with accuracy and repeatability as compared with the method shown in FIG. 17. In FIG. 17, a current electrode 207 is attached to the back of the hand at the base of the index and middle fingers, and a measurement electrode 208 is attached to the top of the wrist. These electrodes are then connected to a healthcare data acquisition device (not shown) for measuring an impedance of the patient. The healthcare data acquisition device as used in the method of FIG. 17, however, is typically bulky and hard to operate. Accordingly, despite the improvements in the art of providing a smaller, lighter and less expensive healthcare data acquisition device such as device 200, there remains an opportunity to make the device even smaller, lighter and cheaper.
Attempts have been made to reduce the size of the electrode structure by using electrodes in contact with the fingertips. This design, however, results in inferior accuracy and repeatability. When the electrodes for applying the current are attached to the fingertips, the resistance value becomes extremely large due to the presence of the joints and the small diameter of the fingers. This results in errors due to difficulty in maintaining a constant current source. Adjacent fingers may at different times be apart or in contact with each other, thereby resulting in a varying current path. As a result, this adversely affects the repeatability and stability of the measurement. As to the prior art method of FIG. 17, the further apart the electrodes are from the measurement device, or the further apart they are from the main current path, the more likely it is that measurement errors and inconsistencies will occur.